http://www.scientificamerican.com/articl...cognition/
EXCERPT: The idea that learning to speak two languages is good for your brain has come to be widely accept as fact, particularly in popular media. Studies have shown that bilingual speakers of all ages outperform monolinguals on certain cognitive performance measures. Other studies show delays in the onset of dementia and some even claim enhanced intelligence. But a handful of attempts to replicate some of these seminal findings have failed to confirm this “bilingual advantage.” The number of studies that have not found a tie between bilingualism and better cognition has risen dramatically over the past few years....
EXCERPT: The idea that learning to speak two languages is good for your brain has come to be widely accept as fact, particularly in popular media. Studies have shown that bilingual speakers of all ages outperform monolinguals on certain cognitive performance measures. Other studies show delays in the onset of dementia and some even claim enhanced intelligence. But a handful of attempts to replicate some of these seminal findings have failed to confirm this “bilingual advantage.” The number of studies that have not found a tie between bilingualism and better cognition has risen dramatically over the past few years....